The Robinsons joyfully land on a planet they think is Earth, but find that they've been tricked by an illusion mist. Vegetable-like trogs trap visitors and drain off their strength. Joining forces with the marooned giant Ptor-Liom, the Robinsons fight free, but the trogs paralyze Ptor-Liom. The Robinsons use their shuttle and their space station to carry him aloft. He's rescued by others of his own kind, and the Robinsons resume their weary way home.

Bill Judd, a new resident of the Moon, is excited to be on a space-suited field trip with his geology class. Walking near the end of the line, he notices that Ann Silva has gone missing -- just as Luna City takes over all voice circuits for announcements. Recognizing that seconds count, Bill retraces his steps, spots Ann trapped in a crevice with her suit leaking air, and jumps down to her. With his help she jumps to safety.